Building a character

Yes, yes, yes!
You are about to start an adventure in the world of role playing!
You are so excited!

You have chosen the world to play in, you have agreed on set of rules, both mechanics of the game and social contract. You even found a game master who will run your session, and that is  no easy feat!

Now all you need is a character.
You sit down and... you draw a complete blank.

Your options are endless,  you can choose to be so many different things that unless you had a very clear idea from the very beginning,  you may not even be able to start.

But you need a character! So you ask friendly Google for help and pick one of the stereotype roles. But... but it just does not feel right. I mean, you can see all stats are probably right, and skill set is what anyone could ever wish for, this is the build that has been used for ages in your world. Yet, you miss something. Your character is not _alive_. Not just yet.
But what to do to turn this character into something fun? What kind of magic mysteriously transforms character sheet into a person?

Start

What I usually do in such situation is I try to come up with one thing that will make this character stand out from other characters I have played - or at least something fun.
Those can be many different things, from small to big. It might be that whenever there is a rat around, your character sneezes. Or maybe he / she has a droopy eyelid or a scar that no one knows how he got.
Or maybe his / her secret hobby is knitting. Whatever, really.

Grow

Then I let the character evolve on its own and show me what this particular person is.
Many,  probably most of my characters were kind of grown organically instead of being built.
Very often I start with one thing only.
One of my characters started as 'an orphan who was very good with cats', another one was a 'bio engineered mercenary with own code of conduct', yet another one was 'a true member of her family, but with unusual for them technical skills'

Not much to start you might think. True, this is not a lot, but it was sufficient for me to start thinking of those characters as of people with, well, own character and skills.
If I can think of absolutely nothing, I often resort to well-known archetypes. Do I feel like playing Xena, the warrior princess? Would a spy be better this time?  Or maybe I should go for a politician?  Everybody's sweetheart?  Mercenary?

Usually one of those archetypes sinks in. It also helps if you know what world you will be playing in, especially if you have choice of where your character comes from - place or family name can add a lot to your new character, if you already know the world and there is some weight to those.

What happens then is a matter of - in a way - character telling me who she is on her own.
How this character handles situations,  how she gets in our out of trouble is what tells me who she is and what she is.

Examples

Remember the orphan character? Not only she turned out to be good with cats,  her trademark became that she could shape-shift into a cat. And her character was that she was very loyal if you earned her friendship - and she did have many friends.
In fact,  story of that particular character was a very long campaign. And yes,  she did change a lot in this time.
Another character being grown: a mercenary, who apart from her profession had only one thing: name of her family. It did not matter until I decided that her motivation will be to strengthen her family (she thinks of herself as of a tool to head of her family). Where this will take her?  We will have to see, this character is still in growing...